I have issues with defrost, The heater has resistance and the t-stat was closed when I checked while the coils was frozen over, I assume this unit does not have a traditional defrost timer and is incorporated the the main control board?
What else can the problem be?
The unit does use the main control board to go through the defrost. Before you replace the board though, this unit also incorporates a defrost thermistor. The thermistor sits at the top of the evaporator coil and is a white bullet looking piece with 2 white wires going into it. The resistance of the thermistor at 0 degrees should be 42.2K ohms of resistance. If not within 10 percent of this resistance then the thermistor is bad and would need to be replaced.